5,275 research outputs found
Effect of Al doping on the optical phonon spectrum in Mg(1-x)Al(x)B(2)
Raman and infrared absorption spectra of Mg(1-x)Al(x)B(2) have been collected
for 0<x<0.5 in the spectral range of optical phonons. The x-dependence of the
peak frequency, the width and the intensity of the observed Raman lines has
been carefully analized. A peculiar x-dependence of the optical modes is
pointed out for two different Al doping ranges. In particular the onset of the
high-doping structural phase previously observed in diffraction measurements is
marked by the appearence of new spectral components at high frequencies. A
connection between the whole of our results and the observed suppression of
superconductivity in the high doping region is established
Sc substitution for Mg in MgB2: effects on Tc and Kohn anomaly
Here we report synthesis and characterization of Mg_{1-x}Sc_{x}B_{2}
(0.12T_{c}>6 K.
We find that the Sc doping moves the chemical potential through the 2D/3D
electronic topological transition (ETT) in the sigma band where the ``shape
resonance" of interband pairing occurs. In the 3D regime beyond the ETT we
observe a hardening of the E_{2g} Raman mode with a significant line-width
narrowing due to suppression of the Kohn anomaly over the range 0<q<2k_{F}.Comment: 8 pages, 4 EPS figures, to be published in Phys. Rev.
Phase equilibria in the La-Mg-Ge system at 500 °c and crystal structure of the new ternary compounds La11Mg2Ge7 and LaMg3-xGe2
The whole 500 \ub0C isothermal section of the La-Mg-Ge ternary system was constructed. The existence and crystal structure of three ternary compounds were confirmed: La2+xMg1-xGe2 (\u3c42, P4/mbm, tP10-Mo2FeB2, 0 64x 640.25), La 4Mg5Ge6 (\u3c43, Cmc21, oS60-Gd4Zn5Ge6) and La4Mg 7Ge6 (\u3c44, C2/m, mS34, own structure type). Five novel compounds were identified and structurally characterized: La 11Mg2Ge7 (\u3c41, P4 2/ncm, tP88-8, own structure type, a=1.21338(5), c=1.57802(6) nm), LaMg3-xGe2 (\u3c45, P 3\u3041c, hP34-0.44, own structure type, x=0.407(5), a=0.78408(4), c=1.45257(7) nm), La 6Mg23Ge (\u3c46, Fm3\u304m, cF120-Zr 6Zn23Si, a=1.46694(6) nm), La4MgGe 10-x (\u3c47, x=0.37(1), C2/m, mS60-1.46, own structure type, a=0.88403(8), b=0.86756(8), c=1.7709(2) nm, \u3b2=97.16\ub0(1) and La2MgGe6 (\u3c48, Cmce, oS72-Ce 2(Ga0.1Ge0.9)7, a=0.8989(2), b=0.8517(2), c=2.1064(3) nm). Disordering phenomena were revealed in several La-Mg-Ge phases in terms of partially occupied sites. The crystal structures of La11Mg2Ge7 and LaMg3-xGe2 are discussed in details. The latter is a 1a3a
7 1a3a
72c superstructure of the LaLi3Sb2 structure type; the symmetry reduction scheme is shown in the B\ue4rnighausen formalism terms. \ua9 2014 Elsevier Inc
Root traits analysis of recombinant inbred lines underlying phosphorus acquisition efficiency in maize.
Cloning and characterization of the gene expression profiles of maize phosphorus-starvation tolerance 1 genes.
Avaliação das características morfológicas do sistema radicular de linhagens recombinantes endogâmicas de sorgo em solução nutritiva sob estresse de fósforo.
Semi-regular sequences and other random systems of equations
The security of multivariate cryptosystems and digital signature schemes
relies on the hardness of solving a system of polynomial equations over a
finite field. Polynomial system solving is also currently a bottleneck of
index-calculus algorithms to solve the elliptic and hyperelliptic curve
discrete logarithm problem. The complexity of solving a system of polynomial
equations is closely related to the cost of computing Groebner bases, since
computing the solutions of a polynomial system can be reduced to finding a
lexicographic Groebner basis for the ideal generated by the equations. Several
algorithms for computing such bases exist: We consider those based on repeated
Gaussian elimination of Macaulay matrices. In this paper, we analyze the case
of random systems, where random systems means either semi-regular systems, or
quadratic systems in n variables which contain a regular sequence of n
polynomials. We provide explicit formulae for bounds on the solving degree of
semi-regular systems with m > n equations in n variables, for equations of
arbitrary degrees for m = n+1, and for any m for systems of quadratic or cubic
polynomials. In the appendix, we provide a table of bounds for the solving
degree of semi-regular systems of m = n + k quadratic equations in n variables
for 2 <= k; n <= 100 and online we provide the values of the bounds for 2 <= k;
n <= 500. For quadratic systems which contain a regular sequence of n
polynomials, we argue that the Eisenbud-Green-Harris Conjecture, if true,
provides a sharp bound for their solving degree, which we compute explicitly.Comment: 27 pages, 4 table
New transcriptional-based insights into the pathogenesis of desmoplastic small round cell tumors (DSRCTs).
To gain new insights into desmoplastic small round cell tumors (DSRCTs) by means of gene expression profiling (GEP). Formalin-fixed, paraffin-embedded surgical specimens obtained from seven pretreated DSRCT patients were interrogated using GEP complemented by immunohistochemistry, a cancer stem cell array, and miRNA in situ hybridisation, including the combined chimera modules miRNA-200/ZEB1 and miRNA-34/SLUG. The chimera modules divided the cases into three classes that respectively recapitulated the traits of mesenchymal epithelial reverse transition (MErT), epithelial mesenchymal transition (EMT), and hybrid/partial EMT. This indicates a close correlation between the reprogramming governed by EMT regulators and DSRCT biology, which was further confirmed by miRNA-21 and is consistent with the broad morphological spectrum of DSRCTs. Starting from the miRNA-200/ZEB1 axis, we also found that DSRCTs carry a signature of immunological ignorance that is not responsive to PD--L1 blockade. Evidence that the up-regulation of miRNA-200 and E-cadherin, and quite a high level of miRNA-21 expression segregate with the MErT supports the idea that, in addition to the hybrid/partial state, MErT is also enriched in stemness: the androgen-positive cases, whose stemness traits were confirmed by stem cell arrays, all fell into these two classes. Our findings also confirmed that tumoral cell PDGFRA expression correlates with desmoplasia, and demonstrated the co-expression of PDGFRA and ISLR/Meflin, another marker of pluripotency. Despite the limited number of cases, these findings provide unexpectedly relevant information concerning the pathogenesis of DSRCTs, and prove the validity of miRNA-based chimera circuit modelling in the clinico-pathological setting
Análise da diversidade do sistema radicular de linhagens e híbridos de milho cultivados em solução nutritiva em diferentes níveis de fósforo.
Markov basis and Groebner basis of Segre-Veronese configuration for testing independence in group-wise selections
We consider testing independence in group-wise selections with some
restrictions on combinations of choices. We present models for frequency data
of selections for which it is easy to perform conditional tests by Markov chain
Monte Carlo (MCMC) methods. When the restrictions on the combinations can be
described in terms of a Segre-Veronese configuration, an explicit form of a
Gr\"obner basis consisting of moves of degree two is readily available for
performing a Markov chain. We illustrate our setting with the National Center
Test for university entrance examinations in Japan. We also apply our method to
testing independence hypotheses involving genotypes at more than one locus or
haplotypes of alleles on the same chromosome.Comment: 25 pages, 5 figure
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